Food web transfer of plastics to an apex riverine predator - Joe D'Souza, Fred Windsor, David Santillo and Steve Ormerod Graduate Ecologist ...
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Food web transfer of plastics to an apex riverine predator Joe D’Souza, Fred Windsor, David Santillo and Steve Ormerod Graduate Ecologist – Arcadis @JDSouza_ Cardiff University Graduate (2018) Joe D’Souza
A Plastic Planet
● Annual global plastic production 350 million tonnes and
another 33 billion tonnes expected by 2050.
● Only a small proportion of plastics ever produced has been
incinerated - most plastics still in use, in landfill or in the
wider environment.
● Research largely focused on microplastics (particles
The Story So Far
● Recent research increasingly shows plastics are
ingested by a range of freshwater organisms, including
macroinvertebrates, fishes and birds.
● Lab studies – lethal and sublethal effects from plastic
consumption.
● Sources, fluxes, behaviour and effects of plastics in
natural freshwater ecosytems poorly quantified.
The Story So Far
● Very little known on the transfer of plastics through
freshwater food webs.
● White-throated dippers (Cinclus cinclus) recognised
indicators of environmental quality, including the
monitoring of organic pollutants.
● Plastics found in roughly half of aquatic invertebrates
used as prey by dippers (Windsor et al. 2019).
Hypotheses
● Using dippers as a model species to assess the occurrence of plastic debris, we
tested three hypotheses:
1. Plastics are transferred from prey to predators in rivers.
2. The concentration of plastic particles increases with urbanisation.
3. Plastics contained in prey are transferred by adults to altricial offspring during
nest provisioning.
The Study
● 15 sample sites across South Wales – Rivers
Cynon, Mellte, Ogmore, Rhondda and Taff.
● Surrounding land use a range of urban, woodland
and grassland pasture.
● Fresh regurgitated and faecal pellets collected
near to where dippers seen feeding.
● Samples (n=166) collected across seasons and a
small number (n=14) from nestlings from two
nests.
Lab Analysis
● Samples analysed under light microscopy, suspected plastics
further analysed using infrared and bright- and dark-field
illumination to distinguish plastics from natural materials.
● Sub-sample (n=72 of 151 suspected plastic particles) analysed
using Fourier Transform Infrared Spectroscopy (FT-IR) at
Greenspeace Research Laboratories (University of Exeter).
● 85% of suspected particles revealed to be plastic polymers.
Results
● Plastics in 47% of faecal and regurgitate samples and at
14 of the 15 sample sites (93%).
● Plastics in both adults and nestlings.
● 95% of plastics were fibres, with fragments and textile
meshes only a small proportion.
● 75% categorized as microplastics (
Results
● Composition of plastics – range of materials, predominantly polyester, polyvinyl
alcohol mixtures and vinyl chloride/vinyl acetate copolymers.
● Urban land use near to sample sites had the strongest effect in increasing plastic
concentrations (t1,100 = 7.48, p = .007; Gaussian GLMM)
● Distance from source had no effect when used as a sole predictor
(t1,108 = 1.33, p = .25).
Findings
1. One of the first studies to illustrate how plastic is being transferred through
food webs in natural freshwater ecosystems.
● Assumption of ingestion via prey supported – size of plastics in samples much
smaller than the normal prey size of dippers.
● Mainly fibres detected (95%) and mainly either polyester, polyvinyl alcohol (PVA)
mixtures or vinyl chloride/vinyl acetate copolymers.
● Potential sources of plastics – textile fibres, textile coatings, reinforced concrete
and construction processes.Findings
1. One of the first studies to illustrate how plastic is being transferred through
food webs in natural freshwater ecosystems.
● Steady-state equation: estimated mean intake of around 200 plastic particles per
day.Findings
2. Concentration of plastics increased significantly along the most urbanised
river reaches.
● Consistent with research linking environmental plastic occurrence with urban land
cover and the amounts of plastics ingested by organisms.
● Urban areas likely to be considerable sources of plastic pollutants, such as:
● Wastewater treatment, ● Increased road density, and
● Combined sewerage overflows, ● Increased volume of plastic
● Direct urban drainage, usage from a range of urban
activities.Findings
3. Plastics present in both adult and nestling samples, demonstrating
intergenerational transfer of plastics.
● Nestlings entirely dependent on adults – again, plastics
appear to be entering via the prey.
● Silver lining – plastics seem to be transient.Future Directions
● Major unknowns remain and prevent effective management.
● Accurate source apportionment needs considerable development at whole
catchment scales.
● Transfer of plastics within food webs have the potential to vector other pollutants
(e.g. contaminants).
● As the ecotoxicological consequences of plastics remains unknown, this global
pollutant continues to increase.Future Directions
● Senedd Climate Change, Environment and Rural Affairs
Committee
● 10-year strategy to reduce plastic use and pollution
● ‘More research is needed to address knowledge gaps in
relation to nano and microplastics in Welsh waters. The
Welsh Government should explore how such research can
be supported, so that its policy interventions are informed
by the latest knowledge’Further Information
● Guardian Article (2020) – Microplastic pollution in oceans
vastly underestimated – study
https://www.theguardian.com/environment/2020/may/22/mi
croplastic-pollution-in-oceans-vastly-underestimated-study
● D’Souza et al. 2020 – Food web transfer of plastics to an apex
riverine predator. https://doi.org/10.1111/gcb.15139
● Windsor et al. 2019 - A catchment‐scale perspective of plastic
pollution.
https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14572You can also read
